Compression deformation of a biaxial stitched glass fibre reinforcement: Visualisation and image analysis using X-ray micro-CT

The compression deformation response of glass fibre reinforcements is generally assumed to be non-linear elastic for the purposes of modelling. In some cases viscoelastic behaviour is also taken into account, while it is only more recently that permanent deformation is being considered. In a previous publication, the authors have showed that significant permanent deformation occurs, and is of comparable magnitude to elastic deformation. It is hypothesised here that permanent (and elastic) deformations in biaxial stitched fabric glass fibre reinforcement occur mainly by means of change of fibre bundle cross-sectional shape and size. Time-dependent deformation is thought to relate to fibre bundle displacement in the direction of compaction loading. Composite laminates were manufactured from a 820 g/m2 biaxial stitched reinforcement material, using different processing parameters. Specimen pieces were cut from the laminates, and the deformation of fibre bundles in these specimens was studied employing X-ray micro-CT technology and image analysis software. The results demonstrate that fibre bundle cross-sections became thinner and elongated, more so under repeated compaction. Fibre bundles were also less undulated in the direction of loading with repeated compaction.